


Less Than Three

by dunked_delirious



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), Ambiguous Relationship, Big Sans, Ecto-Penis (Undertale), Emotional Constipation, Established Friends With Benefits, F/M, Fluff and Smut, Gentle Sex, M/M, Mentions of choking, Morning After, Morning Sex, Other, Plot What Plot/Porn Without Plot, Reader Is Not Chara (Undertale), Reader Is Not Frisk (Undertale), Reader has a vagina, Reader has no defined gender, Shameless Smut, Undertale Monsters on the Surface, Vaginal Sex, an endemic affliction in Underfell, i will never grow tired of this tag, implied birdwatching, magic cocksicle, or at least a Fell monster's version thereof, rise and shine monsterfucker, that also happens to be
Language: English
Status: Completed
Published: 2020-12-07
Updated: 2020-12-07
Packaged: 2021-03-09 23:33:58
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,837
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27924589
Author URL: https://archiveofourown.org/users/dunked_delirious/pseuds/dunked_delirious
Summary: You'd never thought of magpies as your wingmen.
Relationships: Sans/Reader
Comments: 11
Kudos: 76





	Less Than Three

**Author's Note:**

> technically a repost, since i buggered up the original upload in my infinite wisdom. i'm sorry! 
> 
> you know how some people keep a decent filter on their mouth during the day, but then say all kinds of embarrassing crap when they're shitfaced? i get like that within the first few minutes after waking. i like to imagine Red being the same way. 
> 
> this is probably the softest smut i've ever written. if you're here after [Bottoms Up](https://archiveofourown.org/series/1522598) or [Grab the Wall](https://archiveofourown.org/works/23207605/chapters/55558384), this could read as a relationship progression from that. Or it could be a standalone. It's whatever you want it to be.
> 
> i hope this makes your day a little brighter <3

You’re hassled awake by the cranky chattering of magpies.  
  
It is an odd invasion to your senses, thawing through your dreams in increments the way sounds often do. More to the point, it puts an odd spin on the dream in which you are a pirate, homeward-bound for booty with a crew that progressively starts looking more and more corvine, picking up features that ultimately land you on a ship with what looks less like a band of swashbucklers and more like a finalized mass escape of Skeksis from the set of a _Dark Crystal_ reboot.  
  
The cause for it clears up the more you wake, your mind latching on to the incongruity while your other senses cling to the dream, a likely courtesy of the many, many years spent tuning out your noisy neighbors. It’s all rote by now, aided in abundance by a particularly prolific pair housed in the great fir just outside your bedroom window. They’ve been regulars from long before Sans christened your bed, returning duteously each year to rear a new brood of equally talkative young. For just as long, they’ve made themselves known to you through sporadic bursts of tinkling song, and near-inordinate amounts of affront at anyone and anything that strolled within a screeching distance of their nest. And while that in itself may merit admiration, the same could not be said for your mood on the days their bickering robbed you of some precious minutes’ shuteye.  
  
Today, irritation lags behind as you blearily blink yourself awake, less drowsiness than disbelief at the novelty of waking up to something other than an overwhelming urge to pee. Sunlight pours in through the crack between the curtains, casts a chiseled lance of light across the floorboards. The room is swathed in amber light that clues you in on the time before you can slant a glance at the bedside clock, and when you do, you don’t bother fighting off your smile as you sink back under the covers with a happy sigh. 5:24. A good few hours to catch some more z’s, maybe even chase down that sketchy crew of yours. From what little you remember, your voyage was far from over.  
  
You linger in the liminality, adrift on the remnants of your dreams when you feel strong arms cradling you closer, and the hard lines of a familiar grin where it nuzzles at your shoulder. “s’up.”  
  
“Not me,” you mumble, dropping one hand to twine with the bony fingers resting on your belly. The warm huff of his breath tickles your neck, and you wiggle closer with a sleepy smile. Your pirate ship may be drifting ever farther, but the way Sans’s body presses to your back is a treasure worth its weight in gold.  
  
The thoughtful grunt against your neck sounds awfully judgmental. “th’ fuck ya awake fer then?” His voice is throaty and thick with sleep, words drawn taut with a shortage of vowels.  
  
“Magpies were raising a ruckus.” You give his hand a light squeeze and his fingers tighten in return, thumb swiping up to railroad yours into a half-assed wrestle.  
  
The briefest graze of sharpened teeth against your shoulder makes you shiver, closely followed by a thoughtful grumble, “ya got some weird fuckin’ pies on the surface.”  
  
You snort despite your best efforts. The bar on amusement has always been low in the mornings. “Nooo, ‘s not actual pies. Unless you bake them, which you shouldn’t.”  
  
Your thumb caves under the pressure of a bony claw, and Sans asserts his victory by interlacing your fingers. “never said they were.” You manage an inquisitive grunt, and he elaborates, “they’re not pies, they’re ‘pies. as in apostrophe-pies, ya dig?”  
  
You can’t truthfully say that you do, but you’re willing to go along with it in the spirit of camaraderie. His warmth is an underhanded tool of persuasion, reminds you of a sauna but sans the sweltering heat.  
  
“ya smell weird,” Sans mumbles into your neck after a minute’s thoughtful silence. His voice stirs you from a doze you hadn’t realized you’d been slipping back into.  
  
“That would be my morning breath.”  
  
“nah, ain’t that.” He pauses pensively, and you wait patiently for a payoff to the cliffhanger. Almost absently, his free hand drifts down to your thigh, fingers skirting the hemline of your sleepshirt.  
  
“Is it a good kind of weird?” you prompt once it’s apparent you’ll be waiting until kingdom come. You’re not sure what kind of answer you’re expecting, but the warm chuckle against the back of your neck is the only one you need.  
  
“everything about ya ‘s the good kinda weird.” Soft words, ones that couldn’t be wrung out of him with thumbscrews in the light of day, slipping his guard now in a sleep-drunken stupor. Something inside you flutters at that, and you’ve no interest in figuring out why. Your squeak of dissent has little punch behind it, only the same clumsy somnolence that screws with your squirming attempts at turning in his grip. Surely you have your sleep-addled brain to blame for not being particularly bright, because it takes a solid twenty secs of lukewarm thrashing for you to realize there is an upsized asshole skeleton actively foiling your efforts. Your noise of discontent remains unvoiced when his hands begin to wander, sharp fingers raising goosebumps in their wake as they skate over tender skin.  
  
“The fuck’re you doin’,” you manage through a yawn that’s slanted and unsatisfying owing to your mile-wide smile. The puzzled hum from behind you is innocence incarnate, but the devious curl to that grin begs to differ.  
  
“no clue what yer on about,” he rumbles, and any of your inchoate retorts are void at the first prick of sharp teeth against your neck; less a bite than it is a _promise_ , and it makes your breath catch all the same. This is a scene set for two and it’s high time you played your part, lips curling in an incipient smile as you arch your back, leaning into his teasing touches while making sure you push your tush against his pelvis. You’re not the only one who’s gotten well-versed in this spiel. Sans’s mask holds without so much as a bated breath, but there are novels worth of words between the way his hand twists in your sleepshirt that much tighter, and the familiar thrum of rousing magic against your bum.  
  
“You know there’s no way out of this if you pop a boner on me, right?” you slur out between sighs.  
  
Another warm huff against your neck before his hands grow bolder, inch their way up to cup your chest in battered, bony fingers. You whimper when they skim over the bite marks in the tender skin around your nipple: small mercies in light of the ruddy half-moons where his claws had dug into your ass and thighs.  
  
“trust me dolly, ain’t the way out i’m lookin’ for,” he growls against your skin, and there’s no use fighting the shudder that goes through you at the promise in those words. Sans’s hands are rough but his touch is gentle, and you melt into it like countless times before, not bothering to hide your squirming when his thumb moves to rub over your nipple in tight circles, and his other hand slides free to work away at the buttons on your sleepshirt. Not trusting your words to make it past the tailback of whimpers in your throat, you merely shift to grant him better access.  
  
“ya know, ya seemed awful hellbent on wearing this ta bed—” He thumbs at the soft cotton of your collar, “—so i’m thinkin’ it can stay on.”  
  
He isn’t entirely wrong: the reason you’d insisted on throwing on _something_ before conking out in his arms was it being your only shot at either of you getting any sleep. Perhaps there had been better options than a thin shirt reaching to your knee, and nothing underneath. Perhaps you were in denial about how much you had been angling for this outcome.  
  
“Thought you liked to see me in your clothes.” Not that this shirt could be reasonably considered Sans’s any longer. Knowing his unholy war on buttons, you somehow doubt he’ll mourn the loss. Doesn’t mean you’ll pass up a chance to sweeten him up by pressing yourself flush against his pelvis, and when you pry his fingers off a button to guide them to your inner thigh, his sharp intake of air assures you that he’s gleaning every one of your ulterior motives.  
  
“newsflash, kitten, but i also like ta see you out of them.” Hard fingers pinch your nipple and you jolt, your breaths hitching in tandem as you brush against the shapeless magic in his pelvis. “but i think we’ve gone an’ found a loophole ‘round some _stiff_ competition.”  
  
It takes all of half a second to feel the familiar press against your backside, and all you can think of is the amount of conditioning and sheer dedication that ought to have gone into timing one’s boners in with puns. Your vaguely-impressed outrage is outweighed only by frustration with how much you have grown to crave his stupid magic cocksicle. You’re already drawing breath to tell Sans that and more when he does you one better, the hand so unassumingly cradling your thigh slipping away to trail a claw-tipped finger down your slit.  
  
 _“_ _shit._ _”_ His rapt exhale is muffled by your skin as his hips give an involuntary jerk. His touches skirt around your entrance, so close, so torturously teasing, and you can’t stunt the desperation in your voice as you chase them, earning yourself a stuttered groan when his cock rubs up against your lips. “ _fuck,_ do ya wanna—?”  
  
“Please.” Your hand comes up to cup his skull as you draw your leg up over his and arch against him. Sans hisses out another curse, pulling his hand from under your shirt in favor of hooking an arm under your knee—and then you’re the one cursing with your fingers scuffing bone, so used to and still blindsided by the feeling as he fills you, inch by glorious inch. It is still early, you’re still tight and maybe not as wet as you are used to—but your body is warm and pliant and soft with sleep, and you can hear how much he appreciates it from the way he groans into your neck, your skin prickling with the heated gusts of his stuttering, quickened breaths.  
  
The first, tentative thrust is coupled with another graze of teeth against your shoulder, and you’re not sure which it is that has you hiccupping on a moan. Your body bows of its own volition, chasing that delicious pressure, and Sans swears loudly as your head lolls back against his shoulder, fingers tightening on your thigh as he shifts his grip to take you deeper.  
  
“ _Shit,_ Sans,” you hiss, fingers twisting in the sheets in search for something, anything to keep you grounded. The hand not hoisting up your leg delves underneath your sleepshirt, and then you’re jolting with a gasp, your body tensing at the pain-fringed pleasure of a claw tweaking your nipple.  
  
“shit, _shit._ ” His voice is hoarse in your ear, a whisper rife with desperation. “feel good, why the fuck d’ya always feel so _good_ , ain’t fuckin’ fair on me—”  
  
You keen loudly when his thrusts grow bolder; hard, rolling motions that have you feeling every red-hot ridge along his ribbed wonder of a cock. Your fingers slip off his sweat-slicked skull and drop instead to curl into his collar, and the impatient growl against your ear leaves you trembling all over; wired to his voice just as much as to the steady, spirited strokes inside your pussy. You want him to go faster, to hilt inside you hard enough to bruise. You want a face to put to all his happy noises.  
  
“Wanna see you,” you pant out between gasps. Your voice is small and reedy, tangled in the muted slaps of bone on skin and both your breathing—but you feel him nod jerkily against your shoulder before he pulls away, leaving you to whine at the aching emptiness his cock has left behind.  
  
Not that you’re left wallowing for long. The despondency has no time to settle before it leaves you in a startled squeak, the firm hold on your leg sliding to your ankle before you’re effortlessly flipped onto your back, your sleepshirt falling open to bunch softly at your sides and lay you bare before his burning, roving gaze. The sun sifting through the curtains bathes him in the gold of morning light, makes his magic appear near-rosy where it glows in his cheeks, bright and blazing. He shoots you a racy wink as he hitches your legs high and wide, and you cross them behind his head, your flighty giggle trailing off on a sigh when he sinks back inside you.  
  
“You know, Paps will shit a brick when I tell him you were up with the larks for a workout,” you pant, clutching at his shoulders.  
  
Sans slants you an inscrutable glance, mouth twitching in a wry pretense of humor. “he’ll shit a damn chateau when he finds out you talk ‘bout him while we fuck.”   
  
All you have for him is a half-hearted shrug, laudably steady considering you’re all but bent in half, folded like the footstool Papyrus made a point of bringing over the last few times he showed up at your place. Probably in everyone’s best interests that you bow out on the dirty talk with your brain pan’s sudden bent for circling back to the wrong brother. Hardly a lofty task with Sans pressed deep inside you, stealing your words away along with your breath. Dirty silence seems more your speed, what with your brain clinging stubbornly to the dregs of dreamland.  
  
Not like you’ll be going back there anytime soon. Novel as his gentle shtick may be, Sans’s handling makes no allowance for distraction, even in its cutting-edge contrast to the railings that had at some point down the line become a staple in your weekends. You wouldn’t trade the thrill of those frenzied couplings for anything and yet here, at his basest, is how you treasure seeing him the most. His magic burns on those other days, but it is in the quiet mornings that his SOUL shines the brightest, all safe unsullied light filtered through the cage of bone. You’ve never seen the shape of it, not the way another monster would, or perhaps a bond-mate; part of you doubts you ever will. You don’t need that for its formless light to be a mirror of how you see him, hackneyed though it is, beyond all the rough and cracked and crude.  
  
“stop starin’ at it,” Sans huffs, but the twitch that tips his grin is one of mischief. You’d know, you’ve seen them all.  
  
Beats you how, but you manage to match it with one of your own as you slide your hand down to where his is curled into your thigh, settling it atop clawed fingers. “It’s either that or staring at your face, take your pick.”  
  
It's always been one of the weirder blends to witness, the confluence of his scowl cross-linked with pleasure. “keep squawkin’ and the next time you’ll be starin’ at a blindfold.”  
  
That merits a coy wink, and one you offer with a flourish, “That a threat or a promise?”  
  
Your answer comes at you in a reeling thrust, crammed with whatever spite he couldn’t fit in his expression, bundled with a ruthless precision that has you bowing with a broken cry. Getting on his nonexistent nerves falls by the wayside as the rough drag of his cock takes precedence, shadowed in part by the aimless scuffle of your fingers as you arch your hips up, aching, chasing your release with a single-minded zeal that could color Papyrus impressed, and if you could go ahead and come instead of thinking about your blow-buddy’s brother that’d go a long way for some morning mirth—  
  
“come on,” Sans rasps, that gravelly voice a litany, a plea, “i gotcha, yer almost there, squeezin’ me so tight— always so tight when yer close, so _perfect_ —”  
  
His words are a catalyst, a steeping font of current in your circuits that snaps you back and _holds_ , winding you tight, ratchets you higher and higher until that thin thread of forbearance just snaps and you come with a trembling cry, legs locking and nails jabbing into bone as your vision blanks in a blur of blinding white.  
  
It’s not enough to stop him moving, never was, and some days you begrudge him that control. Today, there is nothing you would rather see through the brimming daze of pleasure-tears than that triumphant sneer, no quips you can spare for his quiet complacence as he fucks you through the dwindling aftershocks, and you’re wet, so wet for him that you can feel the warm rush of your slick trailing down your thighs in rivulets.  
  
“Oh _fuck,_ Sans,” you sob out, eyes wincing shut for a moment because it’s all too much, all too much in all the best ways and you never fucking want it to end.  
  
Scarred fingers cup your chin, tipping your face back up to meet his gaze and for a split-beat there is nothing there but softness, every bit of it echoed in touch as he pushes your hands down by your head, and his voice is the same way, gently shushing, “yeah, thassit… jus’ look atcha, takin’ it all…”  
  
Don’t you fucking know it. The slick sounds of him moving inside you still ring through the quiet of the room; your quick, heaving breaths are still being driven out of your chest in tight-drawn huffs. Without the weltering haze of orgasm layered overtop your thoughts, there is room to make note of the strain in his motions, the faintest of wavers to that unswerving smile and the sweat trickling down his skull in ruddy rivulets. The blurred rims of the eyelights that had tracked your every twitch while you were coming stray lower, and there is no disguising the sharper, near-feral gleam in his gaze: Sans loves to watch you, loves watching himself as he fucks you, and now there is nothing to stop you from putting on a show; arching your spine and spreading out wider, easing a fumbling hand between your bodies to slip wetly through the slick of your pussy, peeling apart the lips that are already stretched tight around his girth.  
  
Whatever that does for him is enough, and there is nothing new in what comes next; no warning but the sudden flare of his focal eye erupting with unfettered magic. The broken, choked-off curse that tumbles from his teeth is one you can recognize, though still not understand, and more familiar still is the well of vibrant heat that lights you up from the inside—only this time, you feel it through the barrier of his ribs between you, echoed in the pulsing throb inside his soul. Mindlessly, you bring a hand to rest over his sternum, the better to bask in that glow, and just as quickly Sans snatches it away, the maimed joints of his damaged hand pinching the tender skin over your wrist, adding to the wealth of welts already there as he shudders helplessly against you.  
  
That’s fine, too, because there’s plenty more for you to take in, to _love_ , and after all this time you really, truly do. You love the shutter-shock of pleasure on his face, rampant and ruinous. You love the way he breathes your name as if in prayer.  
  
And you love the way he sags against you when he’s done, even if you’ll one day wind up smushed into the sheets like a sedimentary layer in some exceptionally organic soil.  
  
A venture for another time and place. Today, Sans makes a splash by stirring first, a faint grunt of discomfort shared between you as he carefully withdraws and slumps to lie beside you, his good hand seeking yours out almost unconsciously as he rasps out, “fuck, you’re gonna make a morning monster outta me.”  
  
Once again, there’s no use fighting back your smile. Just barely, you muster up the strength to turn and sling a leg over his, allow deceptively strong arms to pull you closer. Sharp fingertips come up to trail feather-light touches down your spine, the shaky warmth of his breath gusting across your skin the same as those questing fingers.  
  
“Sure beats getting up for a run,” you agree. You shudder at the memory of Boss screeching you awake for a rousing round of crossfit, but keep it to yourself. One mention of his brother is enough.  
  
Recalling that particular blunder brings forth memories of other things, ones that are much more pleasant. Enough, in fact, to send a faint frisson to parts of your body that you know from lived experience will be exceptionally sore, even as you crane your neck to mumble through the doze of afterglow, “I really ought to compliment you on your dick more often.”  
  
A faint chuff of a breath, all exhausted amusement and you would have thought nothing of it, if it weren’t for the gentle fingers settling softly, almost gingerly around your neck. Bemused, you lift your head to meet his gaze and it is strange, because you’ve had it this way before, so many times, but never in the afterglow. There’s nothing even remotely close to choking; only Sans staring at you with those hazy, lazy eyelights. For a split second when the light falls over him just right, you glimpse a monster that is all smooth lines and softened edges, none of the rugged sharpness to put the bite into his smile.  
  
A renewed chatter from the outside snaps him out of it, breaks the spell, and you have no gauge of the emotions that flit across his face, closed off just the wrong side of too fast for you to notice.  
  
Instead, a more familiar smile takes their place, slurring his words to a sleepy drawl, “no skin off my ass, kitten. the faces ya make are compliment enough.” Your own disgruntled snort is muffled into bone as he tucks your head under his chin. “now shut up an’ sleep.”  
  
Even smushed up as you are against an upscale furnace of a skeleton, the idea strikes you as salient and sound. There might be cause to regret it later, your thighs and most assorted parts of you are damp with a charming blend of sweat and come, but it’s nothing a good scrubbing can’t fix and you leave that a predicament for future-you. In the here and now, you are exactly where you want to be, draped over the monstrous form of your already-dozing nutting comrade and listening to the tireless, tinkling puttering of ‘pies.

**Author's Note:**

> as always, thank you for your time. your kindness means the world to me, my starlings. 
> 
> Wherever in the world you are, stay safe and keep your head up.


End file.
